Drag and drop of legacy widgets into blocks works but doesn't render

[draganescu]

Reproduce:

• have the Gutenberg plugin installed and updated to 9.1
• have some non-core widgets (e.g. Astra widgets)
• login into admin and go to Appearance > Widgets
• Add a columns block
• In one of the columns add some text
• Add a legacy widget and pick one of the non-core widgets
• Drag the legacy widget in the columns block
• Save the widgets
• Go to the front-end
• Notice the legacy widget does not show up in the columns

Expected

One of:

a) Can't drag and drop legacy widgets as nested blocks in blocks
b) Legacy widgets render when they're nested inside other blocks

[adamziel]

While it would be awesome to make drag and drop work here, widgets are not really designed with nesting in mind. Think WP hooks, html wrappers, customizer preview and edit icons. Let's prevent drag and drop as an easy fix for starters and keep the discussion open.